Herbicides to Kill Clover in Lawns

by Angela Ryczkowski

White clover (Trifolium repens) is a perennial with a creeping, prostrate habit.

Various species of clover (Trifolium sp., Medicago sp. and Mililotus sp.) occasionally prove problematic in lawns. Covers growing in turfgrass attract bees and reduce the uniformity of the lawn. Additionally, the burs on burclover hurt bare feet and attach to pets or clothes. While clover control in a home garden or landscaped areas is easily achieved by hand-pulling or with mulch application, clover in turfgrass may warrant herbicide control. The best herbicide for a given situation depends on the turfgrass and clover types.

Pre-emergent Herbicides

Pre-emergent herbicides are applied before weed seeds germinate and plants emerge. Herbicides are applied to the soil surface and move into the soil with rainfall or irrigation, where they last for about three to four months. Pre-emergent herbicides are most suitable where annual clovers like burclover are problematic or where clovers have not yet but are poised to invade by seed. Possible herbicide selections for pre-emergent clover control include isoxaben, napropamide, oxadiazon, oryzalin, pendimethalin and pronamide.

Postemergent Herbicides

Postemergent herbicides are applied to the entire lawn or directly on the unwanted clover to kill actively growing weeds. Postemergent herbicides that offer clover control include clopyralid, dicamba, glyphosate, mecoprop, and quinclorac. These herbicides offer the most effective control when applied to young weeds. Glyphosate is a non-selective herbicide that damages any plant it comes into contact with, so it is only suitable for spot treatments, before planting or for turfgrass renovation.

Herbicide Application Considerations

In new lawns, wait until the grass has been mowed at least three times before applying herbicides. Avoid mowing grass for several days prior to applying postemergent herbicides and consider adding a surfactant to foliar herbicide sprays to encourage leaf penetration. Spray foliar herbicides on calm days to avoid drift and do not apply herbicides to drought-stressed lawns or when hot weather is anticipated. Follow label instructions for application. Some herbicides require a permit for use or can only be applied by licensed applicators.

Nitrogen Application

Clovers have a relationship with a bacterium that fixes atmospheric nitrogen, allowing them to fulfill their own nitrogen needs and stay vibrantly green even where nitrogen is lacking. This also allows clovers to out-compete turfgrass in sites with low soil nitrogen. Suspect that nitrogen is low if the turfgrass is yellow but clover remains green. Apply nitrogen fertilizer regularly to promote turfgrass health and prevent or limit the spread of clover into an area. High phosphorus promotes clover invasion, so adjust the fertilizer regimen accordingly.

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